News reports and the group's official blog said 18-year-old Anna Iriyama and Rina Kawaei, 19, were cut on their hands and head. A male staff member was also was cut on the hand.

They were taken to a hospital for treatment.

Police have arrested the attacker, a 24-year-old unemployed man, after the incident in Takizawa city in north-eastern Japan.

AKB48 is a wildly popular song and dance troupe that has spawned affiliates across the country and in Indonesia, China and Taiwan. It has a rotating cast of more than 90 young women known in Japan as "idols".